Interpretive Summary: Economic pressure on the poultry industry has directed the selection process towards fast-growing chickens. Selection based heavily on growth could adversely affect the health of the birds and leave them more susceptible to disease. Our laboratories have been looking at the innate immune system of two lines of chickens (lines A and B) to determine their ability to stay healthy. We have shown increased in vitro heterophil function corresponds with increased in vivo resistance to bacterial infections. Additionally, there is increased mRNA expression levels of pro-inflammatory cytokines/chemokines in heterophils isolated from the resistant line (A) when compared to the susceptible line (B). Collectively, all data indicate there are measurable differences in the innate immune response that are under genetic control. Recently, a small-scale selection trial was begun. We identified roosters within a broiler population with higher and/or lower-than-average innate immune responses and utilized small numbers of roosters to produce offspring with increased or decreased, respectively, innate immune response profiles. This novel approach should allow us to improve chicken breeding stocks by improving the overall immunological responsiveness to produce a line of chickens with an effective immune response which should improve resistance against food-borne microbes, improve responses to vaccines, and increase livability. Ongoing work from this project is providing critical information for the development of poultry lines that will be more resistant to food-poisoning microbes. Use of pathogen-resistant birds by the poultry industry would significantly improve the safety of poultry products reaching the consumer.

Technical Abstract:
Economic pressure on the modern poultry industry has directed the selection process towards fast-growing broilers that have a reduced feed conversion ratio. Selection based heavily on growth characteristics could adversely affect immune competence leaving chickens more susceptible to disease. Since the innate immune response directs the acquired immune response, efforts to select poultry with an efficient innate immune response would be beneficial. Our laboratories have been evaluating the innate immune system of two parental broiler lines to assess their capacity to protect against multiple infections. We have shown increased in vitro heterophil function corresponds with increased in vivo resistance to Gram-positive and Gram-negative bacterial infections. Additionally, there are increased mRNA expression levels of pro-inflammatory cytokines/chemokines in heterophils isolated from resistant lines compared to susceptible lines. Collectively, all data indicate there are measurable differences in innate responsiveness under genetic control. Recently, a small-scale selection trial was begun. We identified sires within a broiler population with higher and/or lower-than-average pro-inflammatory cytokine/chemokine mRNA expression levels and, subsequently, utilized small numbers of high expressing and low expressing sires to produce progeny with increased or decreased, respectively, pro-inflammatory cytokine/chemokine profiles. This novel approach should allow us to improve breeding stock by improving the overall immunological responsiveness, and will produce a line of chickens with an effective pro-inflammatory innate immune response which should improve resistance against diverse pathogens, improve responses to vaccines, and increase livability. Ongoing work from this project is providing fundamental information for the development of poultry lines that will be inherently resistant to colonization by pathogenic and food-poisoning microorganisms. Utilization of pathogen-resistant birds by the poultry production industry would significantly enhance the microbiological safety of poultry products reaching the consumer.